Ext.onReady(function() {
			new Ext.Viewport({
						layout : "border",
						items : [{
									region : "north",
									title : '系统说明',
									height : '100%',
									frame : false,
									width : "100%",
									items : [topPanel]
								}]
					});
		});

var topPanel = new Ext.Panel({
	layout : 'column',
	id : 'mainPanel',
	width : "100%",
	style : 'border-width:0 0 0 0;',
	frame : true,
	height : 450,
	html : '<iframe scrolling="auto" frameborder="0" width="100%" height="100%" src="explainContent.html"> </iframe>'
});
